Problems with redirected stdin and stdout when using py to run python code

I have some python code that runs perfectly when run within python. When I run the code from within matlab using py I appear to have problems with the redirection of stdin and stdout.

The problem can be illustrated with the python code in a file ztest.py:

import os
def ztest():
  os.system(f'./jonesgrid > /dev/null < zxcvbn-split-08.txt')

When run within python, all is well:

>>> import ztest
>>> ztest.ztest()
>>> 

When this is run from matlab with the command

>> py.ztest.ztest()

I get the following output:

At line 283 of file jonesgrid.for (unit = 5, file = 'fort.5')
Fortran runtime error: End of file
Error termination. Backtrace:
#0  0x2aaaaacead1a
<other lines cut>

The file fort.5 has been created together with fort.6. Normally these two files are associated with standard input and output respectively and are not created in the run. I have also tried using subprocess.run() and get the same problem.

I'm not sure whether this should be posted in a python forum or a matlab one, but I'm guessing the problem lies with the way in which matlab is interfacing with python. Other parts of my code that use os.system() that don't make use of redirection work fine.

Answer 1

[Yongjian Feng]

Did you try:

system('python -c "import ztest; ztest.ztest()"')